This invention relates to a liquid-in vibration-isolating device used to support a vibration generating source such as vehicle engine for the purpose of vibration isolation.
A liquid-in vibration isolator, in which liquid is contained inside a body portion equipped with a vibration isolating substrate made of a rubber elastomer, has heretofore been known as a mount supporting a vibration generating source such as vehicle engine so as not to transmit its vibration to a vehicle body and the like.
For example, in an official gazette JP-A-7-77234, a liquid-in vibration isolator is disclosed, wherein a vibration isolating substrate made of a rubber elastomer at one opening portion of a cylindrical body fitting and a diaphragm made of a rubber film at the other opening portion are fitted and adhered under sealed condition, liquid is contained in an inner chamber surrounded by these members, a partition member with an orifice made on the outer circumferential portion being interposed between the vibration isolating substrate and the diaphragm, and being partitioned into a main liquid chamber on the side of the vibration isolating substrate and a sub-liquid chamber on the side of the diaphragm, and both liquid chambers being connected by the orifice formed on the outer circumferential portion of the partition member.
The liquid-in vibration isolating device is used by connecting a boss fitting stuck to an axis center of the vibration isolating device to a vibration generating source side and the cylindrical body fitting to a support side, the vibration damping and vibration isolating functions are fulfilled by the liquid flowing effect between both liquid chambers produced by the orifice and the vibration absorbing effect of the vibration isolating substrate.
As for the liquid-in vibration isolating device, the orifice on the outer circumferential portion of the partition member is normally set so that the dynamic spring rate can be reduced in a relatively low frequency band (10 to 15 Hz) such as shake vibration, effects of reduction of dynamic spring rate cannot be obtained in a relatively high frequency band (100 to 200 Hz) such as fraught sound and the like. For that purpose, as for the liquid-in vibration isolating device, the partition member comprises a partition plate member made of an elastic film at its center portion and an orifice member disposed on the diaphragm side of the partition plate member, hollow space between the center plate portion of the orifice member and the elastic film is formed as a second sub-liquid chamber, independently of the orifice on the outer circumferential portion which passes through the sub-liquid chamber on the diaphragm side and the main liquid chamber, the orifice hole is opened on the center plate portion from the sub-liquid chamber to the second sub-liquid chamber, so as to reduce the dynamic spring rate in both frequency bands of shake vibration and fraught sound.
In such configuration, as the pressure of the main liquid chamber varies due to vibration, mainly vibration in the vertical direction, on the vibration generating source side such as engine connected to the boss fitting, inside liquid flows and liquid in the sub-liquid chamber increases/decreases, and consequently the diaphragm constituting a chamber wall of the sub-liquid chamber approaches the partition member and deforms in the direction of separation.
When the diaphragm is displaced greatly toward the partition member side especially due to load in the direction of compression during this deformation, the diaphragm abuts extensively against the plate surface of the center portion of the partition member, especially against the surface of the center plate portion of the orifice member. Therefore, if the center plate portion of the orifice member is in the form of a plane, it is apprehended that the diaphragm abuts as surface contact to produce hitting sound and falls into the state of adsorption against the plane of the center plate portion to impair the movement of the diaphragm. In particular, when the orifice hole passing through the second sub-liquid chamber is formed on the center plate portion of the partition member, it is feared that the orifice hole is covered to disable its function. Furthermore, there is the possibility of taking scratches on a part of the diaphragm at the opening end of the orifice hole.
Besides, even if the partition member is made up of a single member which does not form the second sub-liquid chamber, similar problems will occur when the center plate portion of the partition member assumes in the form of a plane and the diaphragm abuts on the center plate portion under a load.
If the volume of the sub-liquid chamber on the diaphragm side is set sufficiently large so as not to cause the problems described above, the vibration isolating device itself grows larger, and so it is not preferable from the viewpoint of onboard of a vehicle and the like.
The present invention provides a liquid-in vibration isolating device improved so as not to cause the problems described above.
A liquid-in vibration isolating device of the present invention comprises a cylindrical body fitting, a boss fitting disposed at an axis center of the cylindrical body fitting, a vibration isolating substrate made of a rubber elastomer material interposed between a portion of one opening side of the cylindrical body fitting and the boss fitting to connect both fittings, a diaphragm made of a rubber film fitted and adhered to a portion on the other opening side of the cylindrical body fitting, liquid being contained in an inner chamber surrounded by these members, the inner chamber being partitioned into a main liquid chamber on the side of the boss fitting and a sub-liquid chamber on the side of the diaphragm by a partition member interposed between the vibration isolating substrate and the diaphragm, and both liquid chambers being connected by an orifice formed on the outer circumferential portion of the partition member, wherein multiple convex portions restraining the abutment of the diaphragm against the partition member are provided on at least either an inner surface of the diaphragm, opposed to each other in the sub-liquid chamber, or a plate surface of the partition member. It is preferable that multiple convex portions are provided on a plane opposed to the diaphragm at the center plate portion of the partition member to restrain the diaphragm from abutting.
According to the liquid-in vibration isolating device, multiple convex portions are provided on at least either an inner surface of the diaphragm or a plate surface of the partition member, for example, on a plane of the center plate portion of the partition member, to restrain the abutment thereof when the sub-liquid chamber on the diaphragm side reduces its pressure and gets contracted and the diaphragm approaches and abuts the partition portion, due to large displacement caused by a vibration load in the vertical direction, especially due to load in the direction of compression. Accordingly, since the diaphragm abuts by being scattered under point or line contact conditions at the convex portions and can also be restrained from abutting by surface contact, hitting sound due to abutment is not produced at all and the diaphragm will not become in the state of adsorption on the plate surface of the partition member.
Furthermore, under a condition where the diaphragm abuts the partition member as described above, since space is kept between the diaphragm and the partition member other than the convex portions to secure liquid flow in the sub-liquid chamber, there is no possibility of impairing the function of the diaphragm.
The partition member of the liquid-in vibration isolating device comprises a partition plate member made of an elastic film at the center portion and an orifice member disposed on the diaphragm side of the partition plate member, the orifice connecting the main liquid chamber and the sub-liquid chamber being formed on the outer circumferential portion thereof, a second sub-liquid chamber being formed between the center plate portion of the orifice member and the elastic film, independently of a first sub-liquid chamber on the diaphragm side, and an orifice hole passing through from the first sub-liquid chamber to the second sub-liquid chamber being opened on the center plate portion of the orifice member.
In this case, with the orifice on the outer circumferential portion mainly set for shake vibration and the orifice hole passing through the second sub-liquid chamber mainly set for fraught sound, each dynamic spring rate can be reduced in different frequency ranges such as frequency range for shake vibration and relatively high frequency range for fraught sound and the like, with the result that vibration is effectively damped in a wider frequency range.
And, as mentioned above, when the diaphragm abuts the partition member, the convex portions can restrain the diaphragm from abutting so as not to cause surface contact, hollow spaces can be kept at the portions other than the convexes, and liquid flow in the first sub-liquid chamber can be secured. Therefore, it is not apprehended that the function of the diaphragm is impaired, and the orifice hole is not covered completely or earlier, with the result that the function of the orifice hole can be maintained properly.
Further, since the diaphragm does not come into contact with the orifice hole portion at all, the diaphragm is not broken even if the volume of the first sub-liquid chamber is small, thus the durability can be maintained properly.
As for the liquid-in vibration isolating device of the aforementioned configuration, it is preferable that an opening as the second orifice provided on the center plate portion of the orifice member is provided eccentrically on the opposite side to the position of the interconnecting portion from the first orifice on the outer circumferential portion to the first sub-liquid chamber. Thereby, mutual interference between the orifice on the outer circumferential portion and the orifice hole can be prevented, allowing the characteristics to be stabilized further.
As for the liquid-in vibration isolating device of the aforementioned configuration, multiple convex portions for restraining the diaphragm from abutting are disposed on the center plate portion of the orifice member between the interconnecting portion from the orifice on the outer circumferential portion of the orifice member and the orifice hole, so as to keep the predetermined space along the direction of liquid flow. In this case, even if numbers of convex portions are formed, liquid flow between the interconnecting portion from the orifice on the outer circumferential portion and the orifice hole can be secured properly.
Multiple convex portions for restraining the diaphragm from abutting are disposed on the center plate portion of the orifice member nearly radially centering the orifice hole. Thereby, liquid flow into the orifice hole in the sub-liquid chamber is not impaired, thus the function can be maintained properly.